The present invention relates to a spring for a disc-brake with a sliding caliper, as well as a disc brake equipped with such a spring.
The invention concerns more particularly a multi-purpose spring intended to equip a disc brake, the caliper of which slides relative to a fixed support by means of an axial column.
The U.S. Pat. No. 4,673,065 assigned to the present Assignee discloses a spring for a disc brake of the type comprising a caliper mounted slideably parallel to the axis of a disc rotating on a fixed support by means of at least two axially sliding surfaces formed on the caliper and on the fixed support and held elastically in contact, and two friction members anchored and axially slideable inside an opening of said fixed support, so as to come into frictional contact with the opposing sides of said disc when a brake motor is operated, said spring being mounted elastically inside an opening formed in the arch of the caliper and exerting on the plates carrying said friction members a radial force directed substantially along a radius of the disc and in the direction of the axis of the latter and a tangential force perpendicular to said radial force so as to bias each of the friction members tangentially relative to the circumference of said disc so as to ensure that said members are held in a preferred lateral position.
This known spring is characterized in that it consists of a folded metal blade comprising a mounting portion joined elastically, via its sides located circumferentially at a distance from each other, to two rigid working portions, a first rigid portion extending parallel to the axis of the disc and being capable of elastically biasing, with its two free ends, said carrier plates in a substantially circumferential direction, a second of the rigid portions extending also parallel to the axis of the disc and being capable of elastically biasing, with its two free ends, the carrier plates substantially radially towards the axis of the disc.
With such an arrangement, the spring is held by its mounting portion in the opening formed in the arch of the caliper, its working portions being located in recesses cut in the arch and adjacent to the opening.
The recesses cut in the arch have the effect of reducing the thickness of the latter and hence its strength. The co-pending U.S. patent application Ser. No. 200,756 filed May 31, 88 and assigned to the present Assignee, therefore proposed a spring which was simplified by eliminating the elastic portion and the rigid portion which applies substantially radial forces to the carrier plates. The elimination of these forces could in fact be regarded as acceptable with a certain orientation of the force applied by the other rigid portion of the spring on the bearing surface formed on the side of a projection formed on the peripheral edge of each of the carrier plates, thus modified. The elimination of this part of the spring would enable the recess cut in the arch of the caliper to be reduced so as to give this part adequate clearance, thereby improving the robustness of the brake equipped with such a simplified spring.
However, the elimination of the substantially radial forces on the carrier plates results in the carrier plates having greater freedom of movement, leading, in certain applications, to vibration of the carrier plates, which is transmitted to the caliper, and thus causing considerable noise and premature wear of the friction members and the brake. It has also been noticed that, when the caliper vibrates in this manner relative to the fixed support, the parts of the caliper which come into contact with the fixed support or the locking pin are subject to a certain degree of burring.